Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty [Ritesh]

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, e: 5 };

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
!! obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one month ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested, compared, and the pros and cons of each approach.

**Benchmark Overview**

The benchmark is measuring the performance of four different ways to check if a key exists in an object:

1. `undefined !== obj.d` (test "undefined")
2. `'undefined' !== typeof obj.d` (test "typeof")
3. `'d' in obj` (test "in")
4. `obj.hasOwnProperty('d')` (test "hasOwnProperty")

**Library and Special JS Features**

The benchmark uses the following JavaScript libraries:

* None explicitly mentioned, but we can assume it's running on a vanilla JavaScript environment.

No special JavaScript features or syntax are being tested in this benchmark.

**Comparison of Object Lookup Methods**

Now, let's discuss each comparison method and their pros and cons:

1. **`undefined !== obj.d` (test "undefined")**
	* Pros: Simple and straightforward. No need to check if `obj.d` exists.
	* Cons: May be slower due to the explicit type check. In modern JavaScript, this check is likely to be performed at runtime anyway.
2. **`'undefined' !== typeof obj.d` (test "typeof")**
	* Pros: Similar to the first test but uses the `typeof` operator. This can provide a more accurate result since it checks the type of `obj.d`, not just its existence.
	* Cons: May be slower due to the additional function call and type checking. The `typeof` operator is also slightly less efficient than a simple property access in modern browsers.
3. **`'d' in obj` (test "in")**
	* Pros: Fastest way to check if a key exists in an object, as it uses the property access mechanism under the hood.
	* Cons: May be slower due to the syntax and potential parsing overhead.
4. **`obj.hasOwnProperty('d')` (test "hasOwnProperty")**
	* Pros: Optimized for checking own properties on objects, which can improve performance in some cases.
	* Cons: May not work as expected when `obj.d` is inherited from another object or when using prototype chains.

**Other Alternatives**

Some alternative methods that could be considered:

* Using the `in` operator with the `Object.keys()` method, e.g., `Object.keys(obj).includes('d')`
* Using a library like Lodash's `pickBy()` function
* Using a custom function that checks if `obj.d` exists and returns a boolean value

Keep in mind that these alternatives might not be as efficient or accurate as the original four methods, but they could provide different results depending on the specific use case.

**Benchmark Results**

The latest benchmark results show that the fastest way to check if a key exists in an object is indeed using the `in` operator (`'d' in obj`). However, the results also show some variation between browsers and versions, which can be expected due to differences in implementation and optimization.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36

Browser/OS: Chrome 78 on Mac OS X 10.14.6

View result in a separate tab

Test name	Executions per second
undefined	6313476.5 Ops/sec
typeof	18507128.0 Ops/sec
in	18799714.0 Ops/sec
hasOwnProperty	16725749.0 Ops/sec
bool	18782656.0 Ops/sec

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty [Ritesh] (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool

Created: 4 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one month ago):